Steroids given to premature babies to help them breathe and maintain normal blood pressure may impair the development of a part of their brains, a new study shows.

Researchers found that premature babies treated with the steroid drugs hydrocortisone or dexamethasone had cerebellums that were 10 percent smaller than those of normal newborns. The cerebellum is a region of the brain that plays an important role in motor control, and is also involved in balance, language and behavior.

The researchers did not see the same effect in preemies treated with a similar drug called betamethasone.

The results of the study confirm past research in animals and suggest that national guidelines on the steroids' use should be reconsidered, the researchers said.

"I wouldn't want to say that we just shouldn't use these steroids to help preemies," said Dr. Emily Tam, a pediatric neurologist at the University of California, San Francisco (UCSF) and lead author of the new study. "But I certainly think that these results are an indication that we should be looking for alternative treatments."

The effects of steroids

About 13 percent of all live births in the United States are preterm, meaning the baby is born before the 37th week of pregnancy, according to the Centers for Disease Control and Prevention.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

The AAP currently says that high doses of dexamethasone should not be used on infants, but that there is not enough evidence to make recommendations on the other drugs.

In the new study, the researchers looked at the effects of betamethasone, dexamethasone and hydrocortisone on 172 premature babies admitted to the intensive care nurseries at UCSF and the University of British Columbia between 2006 and 2009. The researchers measured brain growth with magnetic resonance imaging (MRI) scans.

The babies treated with hydrocortisone and dexamethasone had cerebellums that were smaller than those of normal newborns by 8 and 10 percent, respectively, the results showed.

Other regions of the babies' brains appeared unaffected by the drugs, and the researchers did not see any changes in babies treated with betamethasone."This is reassuring because the majority of preemies are exposed to betamethasone rather than other glucocorticoids," Tam said.

The researchers are following the infants up to school age to see what effects this decreased cerebellum will have on their cognitive and emotional development. [Extremely Premature Babies Suffer Cognitive Problems Later]

Surprising results

"The results place clinicians in a difficult conundrum — the steroids can improve lung function, but they could have drastic effects on the brain," said Kevin Noguchi, a professor of psychiatry at the Washington University at St. Louis, who was not involved in the study.

Noguchi, who studies the effects of steroids on rodent brains, said he was surprised by the finding that hydrocortisone impaired the cerebellum's growth, because a protective enzyme in the brain can break down hydrocortisone.

Tam said doctors need to consider other drugs to help treat premature babies. Another possibility would be to find a treatment to give with the steroids that could prevent the drugs from affecting the brain, but not stop them from helping the lungs.

New research in mice from another group at UCSF is showing promising results on this front, she said.